Question

Choose all descriptions that are true for chemical changes.

The identity of the substance stays the same
The chemical and physical properties change during a chemical reaction
Cutting down a tree is an example of a chemical change
There are the same number of atoms before and after the change

Answer 1

The true descriptions for chemical changes are:

1. **The chemical and physical properties change during a chemical reaction** - This is true, as a chemical change involves reactions that result in new substances with different properties.

2. **There are the same number of atoms before and after the change** - This is also true, as the law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction, so the number of atoms remains constant.

The other statements are false:

- **The identity of the substance stays the same** - This is false because a chemical change results in new substances with different identities.

- **Cutting down a tree is an example of a chemical change** - This is false because cutting down a tree is a physical change; it alters the physical state of the tree but does not change its chemical structure.

So, the correct answers are:
- The chemical and physical properties change during a chemical reaction
- There are the same number of atoms before and after the change